Fire control systems utilizing a pressurized fluid such as CO.sub.2 which floods a delivery line, range in size from a single master cylinder to dual master cylinders controlling the discharge of a bank of slave cylinders. Master cylinders are generally actuated either manually, electrically, or pneumatically, or by a combination of methods. In single or dual master systems, it is known to effect actuation using slave backpressure actuators such as those produced by Ansul, and others. However, in these systems, the backpressure actuator is either replaced in order to allow the valve to be used for a master cylinder, or is added to all valve units thus increasing the overall cost and complexity of installation.